What about Daniel's Defiance. Grown only for tase as they do not grow into large offesive weapons such as you find in supermarkets. They will win you no prizes at the show bench.
Alternatively you could look to Pickwick or Hesta which are dwarf varieties.
Always take you beans between 6 and 8ins (your magic 6" ruler = clench your fist then stick your thumb out at right angles to your hand: the distance between the tip of your thumb and the edge of your hand opposite your thumb is 6"......or very close to it).
The commercial offerings are much alike but offer a more colourful alternatives for people like me who grow them on their patio!